Will fouled cylinders clean themselves?

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I just acquired a 20 year old Taurus with a V6 and 186k miles on it.. very inexpensive "a to b" car. 2 of the spark plugs haven't been firing for who-knows-how-long, so four of the pistons look (reasonably) clean when I take out the spark plug and two are just crusty and gross. I don't know what amount of time they've been failing to spark, but the vehicle does have moments when it fires on all 6... about 5 of the 100 miles I've driven it to get it home & begin diagnostics/repairs.

I'm guessing it will need new O2 sensors & cats since those have been eating unburned fuel for a while...

So here's my question: after I repair the ignition problem will the combustion chamber tend to clean itself out? Or is that not a thing that happens?

Advice appreciated.
 
TBH, if it's been misfiring (and getting fuel to those cylinders) for a long time, the engine might be toast. I'd expect those 2 cylinders to have severe piston ring wear from fuel washing the oil off the walls.

Do a compression test on the motor and see what the results are before deciding how to proceed.
 
What rslifkin said. If the engines fine though, absolutely.

Driving should start blasting off crud, especially if you give 'er the beans now and then.
 
I would think the 2 cylinders will clean them selves somewhat once you are firing those cylinder correctly.

I would not do the O2 or cat until you determine the drive train is solid and then only if they are needed.

What kind of emission test does AZ have?

In NY sometime this year they will require all replacement cats to be CARB certified. In some cases the AP & Walker cats are not yet CARB certified and the only replacement is a dealer cat. (Yikes).
 
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Does that have waste spark? Are the 2 on the same coil? I'd be careful on plug choice, copper or double platinum. Single platinum won't work on one of the two plugs.

They should perk back to life when you fix them but like said above their compression could be low and their contribution less than stellar.
 
Originally Posted By: eljefino
Does that have waste spark? Are the 2 on the same coil? I'd be careful on plug choice, copper or double platinum. Single platinum won't work on one of the two plugs.

They should perk back to life when you fix them but like said above their compression could be low and their contribution less than stellar.


I don't believe the 3.8 in the Tauruses ever had any sort of oil pack (always distributor) and the 3.0 didn't get the coil packs until 1996.
 
It's waste spark (3.2L "sho" motor) - the two failing cylinders/plugs are on coil #3 and I've narrowed the ignition failure down to the DIS module or the crankshaft position sensor. I have 3 used DIS modules coming in the mail and 1 new CPS in the mail, have already given the coil pack a twice-over with the ohmmeter and verified that the cam position sensor is pulsing... and done a lot of general wire troubleshooting.

Haven't done compression check yet... but I've only had the car 4 days and work full time so I haven't had many hours to play around yet either.

So, it sounds like if I get the combustion to start happening the crud in there should burn away.. I'll give it an Italian tune-up after it's firing all 6 and then see what the EEC-IV reports & go from there.

Arizona puts pre-OBD2 cars on a dyno and sniffs their tailpipe emissions under load, as well as a cursory visual inspection. I know a couple guys in my county with aftermarket cats so I think they allow aftermarket as long as they were replacing faulty units (as in, you can't legally replace a working one with a "hi-flow" one, but you can replace a broken one with a working one even if that happens to be "hi-flow") - I don't need high performance, just legal (and polite) smog compliance.

Thanks for the tips, guys!
 
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Agree that if you get them firing properly, they'll clean themselves. Which leaves the question of whether the cylinder walls have been damaged after being washed without oil....FYI we had to drive our Wrangler over 200 miles with one cylinder non firing, and it's fine...
 
Once you get it firing properly annd verify things are ok, if it were me, I would do a Seafoam clens of the combustion chamber or some type of overnight soak( Amsoil or similar ). Maybe 2 Seafoam treatments if it is as bad as you say. Help it along and get it out of there faster. Once that is done I would do an OC.
 
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I like the italian tuneup mixed with some fuel system cleaners like Gumout for a short and immediate treatment and then MMO in the gas for a longer treatment.
 
Originally Posted By: badtlc
I like the italian tuneup mixed with some fuel system cleaners like Gumout for a short and immediate treatment and then MMO in the gas for a longer treatment.


+1 This would be my strategy. MMO is good on the upper cylinder lube & clean.
 
The front (nonfunctional) plug is pretty easy to pull, so for my own curiosity I'll be having a look into it at a few steps along the way - I'll see how hard it is to take clear photos through the plug hole. (The only camera I have is my phone... not sure how well it'll do)

Hopefully the parts will arrive this week & I can get started on the weekend.
 
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I wasn't able to get any photos to actually show anything of worth... the camera kept focusing on the exterior of the plug hole instead of through it
frown.gif


But, the vehicle seems to be running very well and the spark plugs in the befouled cylinders look "dusty tan" as they should.. so yay!
 
So did you end up doing anything after fixing the problem i.e. any treatment such as water or seafoam or injection cleaner?
 
Originally Posted By: Vikas
So did you end up doing anything after fixing the problem i.e. any treatment such as water or seafoam or injection cleaner?


I ended up having to remove the intake manifold for another problem (EGR plugged, the EGR tube is bored out of the gigantic aluminum casting of the intake manifold and the whole 35-lb mess has to be removed for cleaning) - so while it was off I did my best at cleaning the whole upper intake manifold, as well as the lower intake ports on their way into the cylinders (though they looked quite clean in the region washed by the fuel injector spray) -


After reassembling everything & restarting the vehicle & getting it warmed up, I used a spacer to hold open the throttle lever on the outside of the throttle body, so that the engine was maintaining ~2700rpm. I then disconnected one of the vacuum ports on the throttle body and gave it a filament straw (left over air tubing from some air shock absorbers) into a bottle of Techron, let that run through which took about 3 and a half minutes total. I then let the engine continue to operate at that RPM with the vacuum hose reconnected where it belongs, then repeated the above process with a large cup of water (just over 5 minutes to drink that) , then let the engine idle. I observed some pretty significant "splat" marks on the driveway behind my exhaust pipes, so one way or another SOMETHING moved from where it was in the engine/exhaust system and out of the tailpipes...

Today I took the vehicle for emissions testing and failed. No check engine light, no OBD codes (I am getting 1-1-1 and 1-0 which is EEC-IV speak for "no problem found")

http://imageshack.us/a/img12/9092/emissionsp.jpg

So.. time to address the problems. High NOX and HC can indicated lean mixture and can indicate ruined cats... uhgn.
 
It could be a faulty EGR valve. That threw my NOX readings off the chart. With a new to me $20 EGR from the wrecker, I was at 10% of the allowable amount. High HC indicates the fuel isn't fully burning. That could be bad plugs or dirty injectors. The Cat could be faulty, if it's been fed raw fuel for a long time it has been doing double duty trying to burn all that fuel and getting super hot. Aftermarket Cats can be found fairly cheap though.

If it's running on all cylinders, nothing cleans out an engine like getting it up to temperature and then driving it hard, preferably up a long hill at high speeds for a period of time. It high cylinder temps will burn off everything. Makes sure when you go for the E-test, the engine is as hot as possible. Drive to the test station like you stole the car, leave it in second gear. The hotter the engine, the better. If someone put a cooler thermostat in the engine, that could cause emissions problems too.
 
The techron/water induction was a good idea, but can also overload the catalyst with too much carbon too fast to burn off. Few hours on the highway it might catch up. Don't think its a manifold cat, so its not that expensive. Is it a bolt on? Can you get it off for an overnight degrease dunk and a pressure rinse? Many times thats all they need to regain efficiency.
 
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